In the general Wiki article about elves, I found two rather keen things.
1) The term 'stroke', in regards to a little bit in your brain going *pop*? Came from saying the person was felled by an elf-stroke. It seemed the most logical, back in the day, to presume that a person lost control of half their body and died due to an invisible elf whacking them with a blow.
2) For those who've read the Dead Witch Walking Hollows books, does this sound familiar to Jenks pixing folks?
The elves are typically pictured as fair-haired, white-clad, and (like most creatures in the Scandinavian folklore) nasty when offended. In the stories, they often play the role of disease-spirits. The most common, though also most harmless case was various irritating skin rashes, which were called älvablåst (elven blow)